Thermally-controlled switch



Patented 24, 1925.'

UNITED STATES PATENT omer..

JOHN E. BROBST, OF SGHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COIPANY, A CORPORATION OF NEW YORK.

THERHALLY-CONTROLLED SWITCH.

application muuugm 11, 1922. serial No. 581,1,

To all lwhom t may comem:

Be it known that I, JOHN E. BRosT, a citizen of the United States, residing in Schenectad in the county of Schenectady, State of ew York, have invented certain new and useful Improvements in Thermally- Controlled Switches, of which the following isa specification.

My invention relates to an arrangement for automatically resetting a thermal responsive device after a switch controlled thereby has been opened by the operation of the thermal responsive device.

Thermal protective relays or -devices are frequently provided which automatically effect the openin of the circuit of a translating device w en abnormal conditions,

such as an overload, occur. A much used form of device of this nature is one which must be manually reset so that the circuit of the translating device may be again closed. This is to insure that the circuit will not be again closed until the operator intends. Thermal relays are used to govern the operation of larger switches which controln the circuit of the translating device, and in such case, two operations are necessary when the switch or switches open in response to the operation of the overload relay-the manual resetting of the overload relay and the manual closing of the switch or switches. This is undesirablesince an etra operation is required, and furthermore, the thermal rela must be placed within convenient reach ofy the operator which is not always possible or desirable.

In accordance with my invention, a connection is provided between the switch in the circuit of the translating device and the thermal responsive device or relay so that the thermal responsive device is reset when the switch opens or at least before the switch is again closed, so that only one operation is required after the switch opens in response to an abnormal circuit condition.

For a better understanding of my invention, reference is had to the accompanying drawing in which Figure 1 shows in my simplified diagram a remote control system for an electrlc motor embodying the invention; Fig. 2 is an end view of a manual starter for a motor with a part of the caslng broken away to show the switch mechanism inside and also showing a thermal rela which is reset b the handle of the switc on the outside o the casin and Fig. 3 diagrammatically illustrates t e connections of the manual starter shown in Fig. 2.

Referring to Fig. 1, the thermal relay or device 10 is adapted to control the manually operated, normally open switch 11 having movable contact mechanism which controls the circuit of a translating device, in this case the electric motor 12. The thermal relay or device 10 is arranged so that it will eect the opening of the line switch 11 in case'the current taken bythe motor 12 is in excess of a certain value for a given length of time. This relay comprises a pivotally mounted member 13 which carries the movable contact 14 which is itself adapted to make engagement with the relatively stationary contact 15. The member 13, and thus the switch contacts, is biased to the open position by the spring 16. The thermostatic element 17 cooperates with the member 13 so as to hold the lcontacts 14 and 15 in engagement as long as conditions in the motor circuit are normal, but in case the motor circuit conditions become abnormal, this thermostat is arranged so that it will flex to the right and thereby permit the switch member 13 to turn counterfclockwise about its pivotal support and thus open the contacts 14 and 15. The closing of the switch 11 is arranged to be under the control of the operator and to be held in the closed position by means of the switch electromagnet through the auxiliary switch 18 and the stop push button. The winding of this electromagnet is controlled by the thermal relay 10 at its contacts 14 and 15, and the arrangement is such-that when the contacts open, the windin of the switch is deenergized and the switch 11 will open in accordancewith its bias. p Whenl this switch 11 opens, it operates the reset push button 19 so as to turn the member 13 of the relay clockwise about its pivotal support and bring the contacts 14 and 15 in engagement. The switch 11 will remainV open, however,

until it is again closed by closing the start push button, and when the switch is closed it will be held closed as before by means of the switch electroma et.

In Fig. 2 I have s own an arrangement in which the line switch 11 and its holding electromagnet are mounted within the casing 20. A pivotally mounted handle 21 on the outside of the casing is provided for manually closing the switchl 11. The thermal relay 10 is shown as being mounted on the outside of the casing 20, but this need not necessarily be the case since in accordance with the invention a thermal relay maybe mounted within the casing out of the reach of the operator.

As illustrated in Fig. 3, the manual starter may .be connected to control the starting and stopping of the motor 12 as Well as to provide automatic time delay overload protection therefor. It will be evident that upon the occurrence of overload conditions in the motor circuit the thermal responsive element 17 is heated suiiciently to release the member 13 and permit the latter to open the contacts 14 and 15 and thereby interrupt the energizing circuit of the holding electromagnet 18. Line switch 11 at once operates to the open position according to its bias and moves the operating handle 21 to the open position.

The push button 19 of the relay. is disposed so that when the handle 21 1s moved to the open position by the opening of the switch 11, the lever 22 will be operated by the projection 23.upon the handle, so as to depress the push "button 19 and thus reset the thermal relay. v

It will be apparent from the above description that no attention need be paid by the operator to the thermal relay, and that this relay ma be located in any convenient place, since i the thermal relay operates to open the line switch 11, the thermal relay is automatically reset when the line switch opens, so that the switch may be reclosed` by the operator turning the handle 21 clockwise without paying any attention whatsoever to the 'thermal relay. This is advantageous, since the number of operations required of the operator is reduced, and he need not 'even know that the translation K device is protected b a thermal relay. The

thermal relay may e located in any convenient place so that connections between the switch and the relay may be provided whereby the relay will be automatically reset when the switch opens, or at least before the switch is again closed. In the arrangement as shown in Fig. 1, the start and stop push buttons need only be located at the station of the operator and the thermal relay may be mounted on a panel with the switch 11 at a remote point.

In accordancewith the provisions of the patent statutes, I have described the principle of operation of my invention, together with the apparatus which I now consider to 'represent the best embodiment thereof, but I desire to have it understood that the appara'tus shown is only illustrative and that the invention can be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States, is

1. In combination, a switch havin movable contact mechanism for contro ling a translating device, a thermal responsive device for controlling the said switch, the said thermal' responsive device having a member biased to one position to effect the opening of the said switch and held in a second position; to effect the holding of the switch in the closed position while the conditions in thecircuit of the translating device are substantially normal, and mechanical connections between the said contact mechanism and the said member for automatically returning the said member to its second position before the switch is reclosed after open- 2. In combination, a switch having movable contact mechanism for controlling a translating device, a thermal responsive device having a member biased to a position to open the switch, a thermostat for holding the said member in the second position to hold the switch closed until conditions in the translating circuit become abnormal and 'to then release the same, and a mechanical connectionl between the said contact mechanism and the said member for returning the member to its second position to be held by the thermostat before the switch is reclosed after being opened by the thermal responsive device.

3. In'combination, a switch having normally opened contact mechanism for controlling a translating device, an electromagnet for holding the switch in the closed position, a thermal responsive device having controlling contacts biased to the o en position in the circuit of the winding o the said electromagnet, thermal responsive means for holdin the said contacts in the closed position w ile conditions in the circuit of the translating device are normal and arranged to release the contacts to open when the translating circuit conditions become abnormal, a resetting element for said thermal responsive means and a mechanical connection between the said contact mechanism and the said resetting element for automatically operating the said element to return the said controlling contacts to the closed position when the said contact mechanism moves to its open position.

4. In combination, normally open switch translating device,

a manually operated for controlling a an electromagnet for 1 holding the switch in the closed position, switch to open, and a mechanical conneca thermal responsive device having nortion between the said switch and the said 10 mally open swltch contacts for controlling contacts for reclosing the contacts when the the said electromagnet, a thermostat for. switch opens 5 holding the said contacts in the closed i- In witness whereof, I have hereunto set tion until conditions in the circuit o the my hand this 9th day of August, 1922. translating device become abnormal and to then release the seme te permit the eeid- JOHN E. BRoBs'r. 

